| Document and Entity Information | Sep. 08, 2021 |
| Entity Listings [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 8, 2021 |
| Entity Registrant Name | Heartland Financial USA, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-15393 |
| Entity Tax Identification Number | 42-1405748 |
| Entity Address, Address Line One | 1398 Central Avenue |
| Entity Address, City or Town | Dubuque |
| Entity Address, State or Province | IA |
| Entity Address, Postal Zip Code | 52001 |
| City Area Code | 563 |
| Local Phone Number | 589-2100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000920112 |
| Common Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $1.00 per share |
| Trading Symbol | HTLF |
| Security Exchange Name | NASDAQ |
| Preferred Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Depositary Shares (each representing 1/400th interest in a share of 7.00% Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series E) |
| Trading Symbol | HTLFP |
| Security Exchange Name | NASDAQ |
